1. Field of the Invention
The present invention generally relates to passenger restraint systems and, more particularly, toward an improved airbag structure.
2. Description of Related Art
Front airbags are conventionally included on both the driver side and the passenger side of the vehicle. The passenger-side airbags 10 are typically formed into a common geometric shape, such as rectangular, oval, etc, such as shown in FIG. 1a. More specifically, the passenger side airbags 10 are typically constructed so as to have a surface, when inflated, facing the passenger that is curved outwardly (convex) toward the passenger, and so as to have an upper end 10a and a lower end 10b that are somewhat narrower than a middle portion 10c of the airbag 10. As shown in the figures, such a convex airbag 10 can have a width at the upper and lower ends 10a, 10b of about 400 mm, while having a width across the middle portion 10c of about 500 mm. However, it has been found that this conventional shape may be disadvantageous in some circumstances.
For example, as shown in FIG. 2a, for a passenger 12 during a high speed impact, the head 12a of the passenger 12 would contact the top portion 10a of the airbag 10. But if the passenger 12 is unrestrained (i.e., not properly wearing a seatbelt as required by law) it may happen that, during a high speed impact, the head 12a of the unrestrained passenger may fail to contact the top portion 10a of the airbag 10. The unrestrained passenger may move to one side so that the passenger's head 12a may directly contact the vehicle's A-pillar 14. The force of the head impact is measured in “Gs” (referring to a correlated multiple of gravitational force). As shown in the graph of FIG. 4, in a collision, a head impact could produce a G spike 18a greater than 50 Gs, which can result in injury to the passenger's head 12a. 
Further, as shown in FIG. 3a, for even a restrained passenger 12 (i.e., one wearing a lap belt) during a high-speed impact, the lap belt does not restrain the passenger's hands 12b. It may happen that the passenger's hands 12b would not directly contact the airbag 10, but would go around and underneath (behind) the lower end 10b of the airbag 10, and directly contact the vehicle instrument panel 16. In addition to causing injury to the hands 12b, such a hard contact can send a G spike through the shoulder and down the chest of the passenger 12, thereby contributing to the other G forces on the chest of the passenger 12 arising from, e.g., the passenger's shoulders. These additional forces can contribute to passenger injuries sustained to the chest.
Both of the aforementioned problems are undesirable and, therefore, there exists a need in the art for an improved airbag structure that eliminates or minimizes the problems experienced in the art.